A first aspect of this invention relates to a tunnel lining comprising a plurality of arcuate segments, a number of which are assembled end-to-end to form a ring which constitutes a part of the length of a tunnel lining, each segment subtending at a longitudinal axis of the lining a respective angle less than 360.degree.. The invention also relates to a method of lining a tunnel with pre-formed segments and to a segment for use in the lining.
It is a common procedure, when boring a tunnel through ground which is not constituted by rock, to line the tunnel as it is bored with pre-formed concrete segments. A number of segments are assembled end-to-end to form a complete, or a substantially complete annulus. A key block may be interposed between two adjacent segments of the ring. The number of segments provided in a ring depends upon the diameter of the lining and is typically five.
Any gap which is present between the exterior of the tunnel lining and the surface of the ground exposed by the boring operation is usually filled with a settable composition referred to in the art as grout. When set, the grout contributes significantly to the stability of the structure. However, it is necessary to ensure that relative movement of the assembled segments does not occur before the grout has set. Thus, it is usual to provide fastening elements for fastening adjacent segments to each other.
One difficulty which arises in the use of fastening elements for fastening adjacent segments to each other is that exact alignment of adjacent segments with each other is often impracticable. A number of arrangements have been proposed for fastening adjacent segments together but these previous proposals suffer from various disadvantages. One object of the present invention is the provision of improved means for fastening together adjacent segments in a tunnel lining.